Consumer appliances can be dangerous when left unattended. For example, the heat generated by an electric iron that is left on and unattended can damage the surface on which it is resting or potentially cause a fire. Other consumer appliances such as curling irons, soldering irons, electric heaters, and the like may also be dangerous if left on in an unattended state, exceedingly more so if oriented in certain positions, e.g., arranged on a heating surface for an electric iron. Accordingly, in the related art, different types of protection circuits have been developed to address these problems. These circuits disable or turn off the appliance if it is not being used and/or is sitting in a potentially hazardous position.
Typical related art methods use a mechanically operated switch driven by gravity or some other acceleration. One type of switch includes a metal ball that is free to roll on a track and comes to rest on a set of electrical contacts at certain angles or under certain accelerations. This type of switch is problematic as it can lose its reliability over time. For example, the mechanical aspects of the switch may corrode over time. In addition, the number of potentially dangerous conditions for which these switches provide useful prevention is narrow due to the mechanical limitations of the switch. The mechanical switch design typically requires a large angle of rotation for the metal ball to move and make contact with the electrical contacts.
Another related method is taught by U.S. Pat. No. 4,203,101, incorporated by reference, which discloses an electric iron having a sensor in the handle that is sensitive to the pressure of an operator's hand. These types of sensors are also limited in their applicability as a user may not want the apparatus to turn off even if the sensor is not triggered.